Hitman Reborn. That ending was just............. What was the point of anything?

Totally I mean seriously

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He has a lot of nerve to say he still doesn't want to be the boss. I mean the assembled the guardians, beat down Xansus from becoming the boss, got the evolved versions of the rings, Knows that is a version of the future he did become the boss, etc. yet after all this he has the nerve to say thanks but no thanks?!? Also it destroys any character development he had as it means he hasn't actually changed at all......

A few others that I can thinkg of

Negima- Seriously such a good manga, so much potential, so much popularity, how did it end up like that?

Magico

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The rushed final battle wouldn't have been too bad and the dues ex machina of the heroin suddenly having magic that she can actually use was weird but tolerable. But that god awful "Final ritual erases everyones memories" crap was beyond stupid. and unlike some other bad endings this one is completely the authors fault. Some endings are bad because of cancellation and other things but this was just a bad idea. What the hell was the point of all that effing character development if you are just going to midwipe everyone? It's almost as bad as saying the whole things was a dream

MxO- Even if the ending was rushed due to cancelation I hate how horribly open ended it is. Not one thing is actually resolved with the plot and the least the author could have done was during the last few chapters have the leading love interest hook up or something. GIve us something that feel like closure!

Tripiece- Not exactly the worst ending ever but it feels like it ended one chapter short. It just ends after the final battle and the MC saying he will apologize to everyone. But they don't show any of it or what even happened to most of the characters. It just feels like it REALLY needed just one more chapter to tie together a few lose ends.